The usefulness of obtaining data concerning temperature, pressure, etc. from the bottom of an oil, gas, or geothermal well during drilling operations, without interrupting those operations, has been recognized for many years. Mud pulse telemetry is a technique which may be utilized to relay such data from the bottom of the well to the operator of the drill string. In a mud pulse telemetry system a pulsing device is incorporated into a drill collar in the vicinity of the drill bit. A fluid, called mud, is circulated through the drill string, and is used primarily to bring cuttings from the drill bit to the surface where they may be disposed of. The pulsing device creates pressure waves in the mud circulating through the drill string, which are received by a transducer at the earths' surface. The pulses are received at the surface in coded form, representing data gathered in the vicinity of the drill bit. Mud pulse telemetry systems are particularly described in U.S. Pat. No. 4,134,100, and U.S. Pat. Nos. 4,323,991 and 4,276,943.
The mud pulse telemetry systems described in the above mentioned patent and applications utilize a fluidic amplifier which directs flow to a vortex valve restrictor means. In designing these fluidic circuits, one is severely limited by the fact that the entire device must fit inside the very confined space of a drill collar. Component response could not be optimizedbecause space constraints were inconsistent with high flow requirements. For example, it is highly desirable to have a relatively small vortex valve diameter, which will yield more rapid response and higher pulse frequencies. Still, it is necessary that the outlet area of the vortex valve be large enough to accomodate the fluid flow which must pass therethrough. While the outlet area must be large enough to accomodate fluid flow, it is desirable that it be small in relation to the valve diameter in order to increase the turndown ratio (ratio of maximum fluid flow to minimum fluid flow through the valve). It is also desirable that the outlet area be relatively small in order to avoid undesirable pressure drops through the fluid amplifier. It is evident that all of these competing considerations can not be simultaneously satisfied using a singular amplifier and vortex valve.
Accordingly, it is an object of the invention to overcome the above named disadvantages and design problems.
It is another object of the invention to provide a fluidic mud pulser system which allows for the use of optimized flow geometries.
It is still another object of the invention to provide a mud pulser which allows for increased frequency response.
Another object of the invention is to increase signal output power of a fluidic mud pulser, and to reduce actuator power requirements.